When I zero a pistol, I shoot it in the position I am most likely to fire the most from. In my case, that's a right-handed modified Weaver stance (old Marine taught me to shoot handguns, so I use the modified Weaver stance, not the Isoceles).
The key, at least for me, is to use all the fundamentals of marksmanship---trigger squeeze, breath control, sight picture, and follow-through---and to make no sight corrections until I have fired at least a group of three, more likely a group of five or six or seven, and established a "group."
In my experience, the biggest mistake shooters make when zeroing a handgun, or any sort of firearm, is to make sight adjustments after only single shots.
Always put at least three rounds downrange before each sight adjustment. And if in doubt, fire a couple of more.
And call all of your shots. Say, out loud, where you think the shot should hit, and compare that to where it actually hits.
hillbilly